1. Field of the Invention
The present invention relates to a system for automatically irrigating and fertilizing of agricultural operations such as groves, truck farms, and the like and more particularly to a computer control system in which feedback from moisture and salinity sensors is provided.
2. Description of the Prior Art
Irrigation and fertilizing of large agricultural operations is expensive and greatly affects the environment. There is a continuing demand to conserve ground water by more efficient irrigation and for a reduction in the pollution of these waters due to fertilizing. An additional economic benefit is achieved when the irrigation water is optimized, and the energy usage and proper amounts of fertilizer are optimized. In the past, it has been common to operate irrigation systems by timing devices which method does not take into account the actual need of the soil for moisture. There have been developed systems which utilize various types of buried sensors to determine when the soil requires irrigation. Typical of such apparatus are those in the following U.S. Pat. Nos.: Hasencamp 2,812,976; Higgins 2,611,643; Sears 3,961,753; and Neal 4,197,866. In general, these systems utilize an in-ground sensor or probe, a threshold device which will turn on the irrigation below a certain indicated moisture level and timers. However, the readings from commonly used moisture sensors are greatly influenced by the salinity of the soil as well as by the moisture. Therefore, the operation of such systems will be influenced by the operator' fertilizing schedule.
In co-pending patent application, Ser. No. 705,719, filed 2-25-85, the present inventors disclose a novel sensor which, when buried in the soil, will permit determination of the salinity level as well as the moisture level of the soil and will effectively separate these two factors.